In disk refiners fitted with refining disks of the above-described type, the material to be refined is treated in a space defined between two refining disks, and the fibers in that material are treated at the location where the ribs or ridges meet one another. Because the ribs meet at an angle to one another as the disks rotate, so-called clip refining occurs. This should be avoided, since it impairs the quality of the treated material.
Attempts have been made to solve this problem by using spaced arcuate ribs or ridges; reference in this regard can be made to U.S. Pat. Nos. 3,674,217 and 4,023,737. It is stated in these prior patents that the fiber material will be worked uniformly when the ribs or ridges are arcuate and that defibration is achieved with the minimum of fiber clipping. These proposals, however, do not provide any real solution to the problem, since the ridges on the two counteracting disks do not meet each other along their full lengths, in spite of this.
The object of the present invention is thus to solve the aforesaid problems and to avoid clip-refining of the material being treated.